Comet 41P Reverses Rotation in 2017 Perihelion

Astronomers have confirmed that Comet 41P/Tuttle-Giacobini-Kresák underwent a dramatic reversal in its rotation direction during its 2017 passage near the Sun, marking the most significant spin change ever observed in a comet. The small icy body, which swung closest to the Sun in April 2017, slowed its rotation from once every 20 hours in March to 46 hours by May before halting entirely and beginning to spin in the opposite direction, completing a rotation every 14 hours by December.

The phenomenon was first detected through observations by NASA's Neil Gehrels Swift Observatory and ground-based telescopes as the comet approached Earth on April 1, 2017. Initial data showed the rapid slowdown, which far exceeded previous records. For comparison, Comet 103P/Hartley 2, the prior record holder, only slowed from 17 to 19 hours over 90 days. In contrast, 41P's change spanned dozens of hours in just two months, a scale that stunned researchers.

Further analysis of images from the Hubble Space Telescope, captured in December 2017 after the comet's perihelion, provided the definitive evidence of the reversal. David Jewitt, an astronomer at the University of California, Los Angeles, who...